In some types of threaded fasteners, advantages can be attained by use of a thread whose pitch is not uniform but varies along the length of the fastener. For example, U.S. Patent Application Ser. No. 6/738,256 filed May 26, 1985 shows several different types of nuts having an internal thread whose pitch increases gradually and progressively and at a uniform rate from one end of the nut to its opposite end. Such a thread of increasing pitch, if accurately dimensioned, can improve the distribution of axial load forces between different turns of the thread when the fastener is in use, and can also provide a self-locking action. However, it is difficult from a practical standpoint to determine with conventional gauges whether a varying pitch thread is in fact accurately dimensioned. Gauges of the type normally employed in measuring standard threads of uniform pitch can not easily check the accuracy of a thread of varying pitch, and yet proper gauging of a thread in production is an absolute requirement for many purposes such as high performance applications in the aircraft industry.